Linux Operating system
•It is a system software which provides
an interface between user, hardware, peripherals devices and application
program. Every os consists
of two components
•Kernel
•shell
Kernel
•It is core of an operating system, it
is an interpreter between user and hardware. In Dos – 10.sys, msdos.sys, in xp –
NTUSKRMI32.com, in linux – Vmlinuz.
•Shell
•Shall is a command line interface
(interpreter) between user and kernel. In Dos, winxp,
win7,2k8, 2k3, vista – command.com
•In linux and unix – bash, csk,ksh,tcsh.
Types
of operating system
•There are 3 types of operating system.
1.Single user single task – in
this os a single
user log in an perform a single task
Ex. Dos
2.Single user multitask – in
this os include
all type of desktop os which
log in a single user and perform multitask.
Ex.
Xp,win7, ubuntu
3.Multi user multi task – in this
os more
than one user can log in from the
different terminals and perform multiple task.
Ex.
Server 2000,2003, 2008, Redhat
Enterprise Linux,etc.
File System Structure In Linux
•1. / – Root
•It is a home folder of
an administrative account in linux
Every single file and directory starts from
the root directory.
Only root user has write privilege under this
directory.
2. /bin – User Binaries
•It store all the
binaries files
Contains binary executables.
Common linux commands
you need to use in single-user modes are located under this directory.
Commands used by all the users of the system
are located here.
For example: ps, ls, ping, grep, cp.
•3. /sbin – System Binaries
•It store all the
system binaries
•All the adminsitrative commands such as user add user mode, user del, grp del & grp add etc
Just like /bin, /sbin also
contains binary executables.
•4. /etc –
Configuration Files
Contains configuration files required by all
programs.
This also contains startup and shutdown shell
scripts used to start/stop individual programs.
For example: /etc/resolv.conf, /etc/logrotate.conf
•5. /dev – Device Files
•It is store all the
hardware access point .
Contains device files.
These include terminal devices, usb, or any
device attached to the system.
For example: /dev/tty1, /dev/usbmon0
•6. /proc – Process Information
•It stores all the virtual file system , process in the system
Contains information about system process.
7. /var – Variable Files
var stands
for variable files.
Content of the files that are expected to grow
can be found under this directory.
This includes — system log files (/var/log);
packages and database files (/var/lib);
emails (/var/mail);
print queues (/var/spool);
lock files (/var/lock);
temp files needed across reboots (/var/tmp);
•8. /tmp – Temporary Files
Directory that contains temporary files
created by system and users.
Files under this directory are deleted when
system is rebooted.
•9. /usr – User Programs
•It store user
documentation and manual pages.
Contains binaries, libraries, documentation,
and source-code for second level programs.
/usr/bin
contains binary files for user programs. If you can’t find a user binary under
/bin, look under /usr/bin. For
example: at, awk, cc,
less, scp
/usr/sbin contains
binary files for system administrators. If you can’t find a system binary under
/sbin, look
under /usr/sbin. For
example: atd, cron, sshd, useradd, userdel
/usr/lib
contains libraries for /usr/bin and
/usr/sbin
/usr/local
contains users programs that you install from source. For example, when you
install apache from source, it goes under /usr/local/apache2
•10. /home – Home
Directories
•It is store the home
directory of the local user account with there name .
Home directories for all users to store their
personal files.
For example: /home/john, /home/nikita
•11. /boot – Boot
Loader Files
it stores booting files of the operating system
Contains boot loader related files.
Kernel initrd, vmlinux, grub
files are located under /boot
12. /lib – System Libraries
It store all the library files
Contains library files that supports the
binaries located under /bin and /sbin
Library filenames are either ld* or lib*.so.*
For example: ld-2.11.1.so, libncurses.so.5.7
•13. /opt – Optional
add-on Applications
opt stands for optional.
Contains add-on applications from individual
vendors.
add-on applications should be installed under
either /opt/ or /opt/ sub-directory.
•14. /mnt – Mount Directory
Temporary mount directory where sys admins can
mount filesystems.
•15. /media – Removable
Media Devices
Temporary mount directory for removable
devices.
For examples, /media/cdrom for
CD-ROM; /media/floppy for floppy drives; /media/cdrecorder for CD
writer
•16. /srv – Service Data
srv stands
for service.
Contains server specific services related
data.
For example, /srv/cvs contains
CVS related data.
swap
partition
•The swap partition is the portion of
the hard drive that linux uses as
virtual memory when it runs out of physical memory.
•Swap partition is a dubal of the
RAM
